Disclosed are high stability ink delivery system systems and methods for their use, in which a secondary reservoir is placed upstream of a printhead. The secondary reservoir can be opened to the atmosphere through a valve, such as based on the reading of a pressure sensor placed at a point before the printhead. The purpose of this valve is to open the secondary reservoir to the atmosphere when the pressure sensor indicates that the secondary reservoir can be open while avoiding air aspiration, and closing it when this condition is not satisfied.
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14. An ink delivery system for a printing system that includes a printhead through which ink is jettable, the ink delivery system comprising:
a reservoir in which ink is stored, at least temporarily, before being jetted through the printhead;
a sensor that is configured to
measure pressure within a conduit through which the ink travels from the reservoir to the printhead, and
output a signal that corresponds to the measured pressure;
a valve that is fluidly connected to the reservoir and configured to be dynamically and controllably opened to atmosphere based on the output signal, to maintain stability as the measured pressure changes as the ink is jetted through the printhead as part of a printing operation.
1. An ink delivery system for a printing system, the ink delivery system comprising:
a pressure sensor that is positioned on an ink delivery conduit upstream of the printhead interconnected between a secondary ink reservoir in which ink is stored and a printhead through which the ink is jettable, the pressure sensor being configured to
measure pressure within the ink delivery conduit when the printing system is printing, and
output a signal corresponding to the measured pressure; and
a valve that is fluidly connected to the secondary ink reservoir;
wherein the secondary ink reservoir is configured to be opened to atmosphere through the valve, based on the output signal of the pressure sensor, to maintain stability as the measured pressure changes when the printing system is printing.
8. A printing system comprising:
a controller;
one or more printheads, wherein each printhead includes one or more inkjets having nozzles for jetting ink onto a workpiece based on a signal received from the controller;
a supply assembly for storing and delivering the ink to the one or more printheads, wherein the supply assembly includes:
a primary ink reservoir;
an ink delivery conduit for transferring the ink from the primary ink reservoir toward the one or more printheads; and
an ink delivery system including:
a secondary ink reservoir located between the primary ink reservoir and the one or more printheads;
a pressure sensor positioned on the ink delivery conduit upstream of the one or more printheads, the pressure sensor being configured to
measure pressure within the ink delivery conduit when the printing system is printing, and
output a signal corresponding to the measured pressure; and
a valve via which the secondary ink reservoir is configured to be dynamically opened to atmosphere, based on the output signal of the pressure sensor, to maintain stability as the measured pressure changes when the printing system is printing.
2. The ink delivery system of
3. The ink delivery system of
4. The ink delivery system of
5. The ink delivery system of
6. The ink delivery system of
7. The ink delivery system of
9. The printing system of
10. The printing system of
11. The printing system of
12. The printing system of
13. The printing system of
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This application is a continuation of U.S. patent application Ser. No. 16/162,077, filed on Oct. 16, 2018, which is incorporated herein by reference in its entirety.
At least one embodiment of the present invention pertains to an inkjet printing ink delivery system. More specifically, at least one embodiment of the present invention pertains to a high stability ink delivery system for an inkjet printing system.
Ink delivery systems have as main tasks delivering ink to printheads, ensuring that the conditions at the printhead nozzles are the desired ones for the drop ejection process, compensating the perturbations induced by the ink discharge, and ensuring the long-term robust performance of the printheads. With scanning or multi-pass printers, the robustness issue is not as critical because the multiple passes minimize the chance of apparition of printing defects in the final image.
For single-pass printing applications, system robustness is critical, because any printing defect will be present in the final product. In these applications, improved robustness has been traditionally sought by inducing a continuous flow of ink through the printheads, such as to prevent temporal or permanent nozzle obstruction induced by foreign particles or air bubbles. Due to the different requirements of different printing platforms and applications, such ink delivery systems have evolved into different configurations that aim to give the best balance in terms of performance, robustness, complexity and cost.
To allow closure of the hydraulic system, the number of actuators in the ink delivery system should be at least equal to the number of variables to be controlled. In a non-recirculating ink delivery system, the pressure at the printhead nozzles, also called meniscus pressure, must be controlled, to control the drop ejection process. A basic method to achieve this is through the use of a closed pressurized reservoir. However, such systems are very rigid, because they do not allow to change the meniscus pressure, and often require frequent replacement of reservoirs or cartridges.
Alternatives or variations to such basic systems include configurations in which the meniscus pressure can be changed, based on hydrostatic pressure, through the use of multiple interconnected reservoirs. In some such embodiments, a pump is configured to set the air pressure within the ink reservoir and, consequently, the meniscus pressure. In some alternate systems, a mechanically movable ink reservoir allows for the control of meniscus pressure by changing its vertical position with respect to the printhead. In other configurations, a siphon is connected to the supply manifold, in which the atmosphere is employed, to prevent ink exhaust.
In industrial printers, where single-pass printing is preferred due to its higher productivity, the use of ink recirculation is commonly used. A simple configuration to achieve ink recirculation can be achieved by modifying a hydrostatic-based non-recirculating ink delivery system, to include an ink return path. Such a system can be based on two tanks that are open to atmosphere, where the height difference between them, and the height of the ink free surface, defines the recirculation flow rate and the meniscus pressure. While such a system is intrinsically very rigid as these parameters cannot be adjusted, the system may include the abovementioned enhancements. For example, in some such systems, a valve can be placed upstream of the printheads, to control the meniscus pressure, while in other such systems, the control of meniscus pressure is achieved by using a pump downstream of the printheads.
Nevertheless, in industrial applications, it is preferred to be able to independently set the meniscus pressure and the recirculation flow rate, to decouple the requirements in terms of drop jetting and robustness, so at least two actuators are needed. Two main philosophies can be followed to achieve this:
In principle, the first approach has better stability, due to its reliance on hydrostatic pressure, but also becomes more costly and complex compared to the second approach, due to the higher number of actuators that have to be integrated. The decision about which such approach to choose becomes of paramount importance for the cost of the machine, its complexity and operational cost and the design requirements that have to be imposed to the associated subsystems, like the electronic control system, particularly when combined with high discharge printheads.
Some current single-pass printers include an ink delivery system having two pumps: one (filling pump) placed before the printheads, and another (meniscus pump) placed after the printheads. These two pumps or actuators allow to independently control the flow rate through the printheads and the meniscus pressure, to improve the robustness of the system for single-pass printing applications, without affecting the drop ejection process.
One or more embodiments of the present invention are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements.
References in this description to “an embodiment”, “one embodiment”, or the like, mean that the particular feature, function, structure or characteristic being described is included in at least one embodiment of the present invention. Occurrences of such phrases in this specification do not necessarily all refer to the same embodiment. On the other hand, the embodiments referred to also are not necessarily mutually exclusive.
Introduced here are techniques that can be used to improve stability for ink delivery systems, particularly for high discharge applications, such as under conditions in which the volume of ink that is jetted through the printheads is comparable to the volume of ink that is otherwise recirculated through the system, when the system is not printing.
Various exemplary embodiments will now be described. The following description provides certain specific details for a thorough understanding and enabling description of these examples. One skilled in the relevant technology will understand, however, that some of the disclosed embodiments may be practiced without many of these details.
Likewise, one skilled in the relevant technology will also understand that some of the embodiments may include many other obvious features not described in detail herein. Additionally, some well-known structures or functions may not be shown or described in detail below, to avoid unnecessarily obscuring the relevant descriptions of the various examples.
The terminology used below is to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific examples of the embodiments. Indeed, certain terms may even be emphasized below. However, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such.
A common problem in current printing systems is the stability of the ink delivery system in high discharge applications. In such applications, the volume of ink that is jetted through the printheads is comparable to the volume of ink that is being recirculated through the system when it is not printing. The severity of the perturbation induced by the sudden discharge of ink through the printheads can impose stringent constraints on the dynamics of the system, which can include the hydraulic circuit, the actuators or pumps, and their respective control electronic systems.
Certain embodiments of the high stability ink delivery system disclosed herein are configured to prevent the pressure at the printhead nozzles, i.e., the meniscus pressure, to reach a value outside of the operating window, such as to prevent conditions such as uncontrolled drop formation, i.e., dripping, and/or ink starvation.
The illustrative print system 12a seen in
As further seen in
One of the advantages of this mode of operation is that the high stability ink delivery system 50 can readily be configured work with positive and/or negative pressure values before the printhead 24, thereby allowing a wide range of recirculation flow rate and/or meniscus pressure values to be defined.
For instance, under normal conditions, a pressure setpoint 67 can be established for the pressure as measured by the pressure sensor 64 that is located before the printhead 24, i.e., upstream of the printhead 24, wherein the pressure setpoint 67 ensures that the reservoir 56 can controllably be opened to the atmosphere 58, as defined by the control system 62, 34 that governs the pumps or actuators 48 and/or 68, in order to benefit from the superior stability achieved by the fact that the pressure before the printhead 24 is defined based on the hydrostatics in the secondary reservoir 52.
As seen in
In the illustrated embodiment, the processing system 600 includes one or more processors 605, memory 610, a communication device and/or network adapter 630, and one or more storage devices 620 and/or input/output (I/O) devices 625, all coupled to each other through an interconnect 615. The interconnect 615 may be or include one or more conductive traces, buses, point-to-point connections, controllers, adapters and/or other conventional connection devices. The processor(s) 605 may be or include, for example, one or more general-purpose programmable microprocessors, microcontrollers, application specific integrated circuits (ASICs), programmable gate arrays, or the like, or a combination of such devices. The processor(s) 605 control the overall operation of the processing device 600. Memory 610 and/or 620 may be or include one or more physical storage devices, which may be in the form of random access memory (RAM), read-only memory (ROM) (which may be erasable and programmable), flash memory, miniature hard disk drive, or other suitable type of storage device, or a combination of such devices. Memory 610 and/or 620 may store data and instructions that configure the processor(s) 605 to execute operations in accordance with the techniques described above. The communication device 630 may be or include, for example, an Ethernet adapter, cable modem, Wi-Fi adapter, cellular transceiver, Bluetooth transceiver, or the like, or a combination thereof. Depending on the specific nature and purpose of the processing device 600, the I/O devices 625 can include devices such as a display (which may be a touch screen display), audio speaker, keyboard, mouse or other pointing device, microphone, camera, etc.
While the high stability ink delivery system 50 can readily be implemented for a wide variety of inkjet industrial printers 12, it should readily be understood that the delivery system 50 also be configured for other ink and fluid delivery systems.
This high stability ink delivery system 50 makes possible the introduction of robust high discharge solutions in current single-pass printer platforms with minimal modifications of the ink delivery system and minimal cost and complexity increase. As a result of this, a wide variety of printers related to inkjet printing can benefit from such systems and methods for their use, such as for digital application of coating and varnish, texturing and additive manufacturing.
Unless contrary to physical possibility, it is envisioned that (i) the methods/steps described above may be performed in any sequence and/or in any combination, and that (ii) the components of respective embodiments may be combined in any manner.
The ink delivery system and printer system techniques introduced above can be implemented by programmable circuitry programmed/configured by software and/or firmware, or entirely by special-purpose circuitry, or by a combination of such forms. Such special-purpose circuitry (if any) can be in the form of, for example, one or more application-specific integrated circuits (ASICs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), etc.
Software or firmware to implement the techniques introduced here may be stored on a machine-readable storage medium and may be executed by one or more general-purpose or special-purpose programmable microprocessors. A “machine-readable medium”, as the term is used herein, includes any mechanism that can store information in a form accessible by a machine (a machine may be, for example, a computer, network device, cellular phone, personal digital assistant (PDA), manufacturing tool, or any device with one or more processors, etc.). For example, a machine-accessible medium includes recordable/non-recordable media, e.g., read-only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; etc.
Those skilled in the art will appreciate that actual data structures used to store this information may differ from the figures and/or tables shown, in that they, for example, may be organized in a different manner; may contain more or less information than shown; may be compressed, scrambled and/or encrypted; etc.
Note that any and all of the embodiments described above can be combined with each other, except to the extent that it may be stated otherwise above or to the extent that any such embodiments might be mutually exclusive in function and/or structure.
Although the present invention has been described with reference to specific exemplary embodiments, it will be recognized that the invention is not limited to the embodiments described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense.
Escudero Gonzalez, Juan, Bueno Espinal, Eduardo
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